In Germany we have "Retard-Tabletten" (Tabletten = pills), which are not intended to stop (or accelerate) cognitive decline, but release the active ingredients with a delay.

We have those too. I wonder how many people actually know that's what that means, cause it's not an everyday word by far here in this meaning.

If you work with engines or planes you should be familiar with it's non-slur meaning. You retard ignition timing (you also "pull back" ignition timing) and you retard the throttles. Airbus planes tell you specifically to "retard".